The present invention is directed to an apparatus for helping one mold half mate with another mold half and more particularly to a mold interlock or locking device.
Molds, such as those used in injection molding, typically include two mold halves that can each be equipped with a mold cavity used to make some part. During molding, relative movement between the mold halves bring the two halves together. A moldable material, such as a plastic, a resin, or the like, is injected into each cavity. After the moldable material has had a certain amount of time to set, the mold halves are separated and the molded part is ejected.
This process typically does not take very long. For example, in some molding application, the complete cycle time to make a molded component can be as little as a couple of seconds.
Molds are equipped with mold interlocks that help ensure accurate alignment and guidance of the mold halves during mold setup and later when they are repeatedly being brought together during operation. Such locks are also intended to help ensure guidance between mold cores and stripper inserts, when such mold components are used.
Typically, each mold has four such interlocks with an interlock located along each side of the mold. Each interlock includes a head, or male portion, that is attached to one mold half and a receptacle, or female portion, that is attached to the other mold half. When the mold halves come together, the head of each interlock is received in its respective receptacle helping to ensure accurate mating of the mold halves.
During mold setup, interlocks are attached to the mold halves at parting line and one mold half is brought into mating contact with the other mold half When mated, the head of each interlock is received in its respective receptacle. Various components of the mold are thereafter adjusted to locate the mated mold halves relative to each other. This helps ensure smooth, fast and accurate operation of the mold during molding operation.
During molding operation, as the mold halves are brought together, the head of each interlock is received in the receptacle. The receptacle has one or more sidewalls that guide movement of the head as it enters and moves into the receptacle. As the head enters and moves into the receptacle it helps guide the mold halves together to ensure that that they accurately mate with each other. By helping to ensure accurate mating, mold interlocks help correct or compensate for slight misalignment between mold halves. This also helps ensure that mold cavities accurately overlie each other during molding and that the mold cavity shut-offs properly align.
One very common type of mold interlock is a side lock. A side lock has a head that extends outwardly from a horizontal mounting base that is of square or rectangular cross section. The head is defined by straight sidewalls that are typically generally perpendicular to the base. During operation, the head is received in a receptacle that is defined by a pair of straight sidewalls that are generally parallel to the straight sidewalls of the head.
Side locks are simple to use and install. They typically designed with an angular clearance of zero degrees and a dimensional clearance of between 0.0002 and 0.0004 inch between the head and the receptacle. They also allow for thermal expansion of the mold halves when properly installed. Zero clearance locking fitting typically is not required.
They are not without drawbacks. Their relatively narrow clearance means that they can bind if not opened in parallel, which can occur if there is some misalignment. These types of locks give little protection to smaller angle shut-offs, which can lead to shut-off misalignment or clashing. They usually need lubrication, which means that they cannot be used in certain medical and food component molding applications where lubricants typically cannot be used. Even when lubricated, metal to metal contact between the head and receptacle often result in excessive wear because any lubricant is often wiped during mold operation.
Another common type of lock is a rectangular tapered interlock. They are similar in construction to a side lock, except that its head is longer and its sidewalls tapered. While its sidewalls that define its head are straight, each sidewall has a taper angle of about 10xc2x0 from perpendicular. Each sidewall of the receptacle in which the head is received is complementarily tapered. This type of lock is machined into both cavity mold halves at parting line and adjusted to laid zero clearance by grinding the overall height of the head.
This type of mold interlock is easy to install, provides a larger contact area, and accommodates greater mold misalignment than does a side lock. However, it too suffers from many of the drawbacks of side locks. For example, its tapered straight sidewall construction provides little protection to relatively small angle shut-offs. As a result, shut-off misalignment or clashing can undesirably occur. Lubrication can also be a problem. This can limit its use and lead to premature replacement due to excessive wear.
A still further type of mold interlock is a tapered round interlock. It has a head defined by a tapered, conical sidewall that is received in a complementary receptacle. Its application is limited because it does not accommodate thermal expansion and provide little protection for smaller angle shut-offs.
What is needed is a mold interlock that does not suffer from at least one or more of the aforementioned drawbacks. What is also needed is a mold interlock that is more economical to use.
The present invention is directed to a mold interlocking device that includes one portion that is attached to one mold half that has a head that is received in a pocket in a receptacle of another portion that is attached to the other mold half In one preferred embodiment, the head has a sidewall with at least one channel in it for receiving an insert that facilitates insertion of the head into the pocket when one mold half is being brought toward the other mold half. In another preferred embodiment, the head includes a pair of spaced apart and generally parallel sidewalls that has a tapered section disposed between a straight section and a mounting base from which the head extends. The pocket is defined by sidewalls of complementary contour. In a still further it preferred embodiment, the head includes a second tapered section that is located between its free end and the straight section.
In one preferred mold interlock embodiment, the head has a pair of spaced apart sidewalls that each have a plurality of channels therein. The head extends outwardly from the mounting base and the base is removably mounted to a mold half An insert is received in each channel. Preferably, a portion of each insert extends outwardly beyond the sidewall in which it is disposed so that it can make contact with a sidewall of the pocket during insertion of the head into the pocket. In a preferred insert embodiment, each insert comprises a roller that is capable of rotation relative to the head. In one preferred roller embodiment, each roller comprises a needle bearing. In one preferred embodiment, each sidewall has three channels with a roller disposed in each channel.
Each channel is comprised of a pair of generally parallel lips that curl slightly around a roller received in the channel to retain the roller. Preferably, the channel and the lips are constructed such that at least about one-quarter of the roller surface is exposed. Each lip is constructed to provide a slight amount of clearance to facilitate rotation as well as to permit lubricant on a roller to pass between it and the roller. Additional clearance between the channel and the roller interiorly of the lip so as to provide a reservoir for lubricant. This reservoir helps lubricate and thereby increase the life of the roller.
The head includes a pair of spaced apart endwalls that bracket the sidewalls. Each channel preferably has an entrance in at least one of the sidewalls to permit insertion of a roller therein. A stop prevents withdrawal of the roller once it has been inserted. A preferred stop embodiment is a plate that is removably attached to the sidewall. If desired, the channel can extend through both endwalls and a pair of such stop plates can be used to retain rollers in their respective channels.
The channels are located in a straight section of each sidewall, which preferably are generally parallel to each other. Each sidewall preferably further includes an tapered section disposed between its straight section and the mounting base. The tapered section is outwardly tapered such that the head is wider adjacent the mounting base than adjacent its free end. When the head is inserted into the pocket, each tapered section preferably bears against a portion of a pocket sidewall to help ensure that a positive interlock is achieved.
The receptacle includes a pair of spaced apart upstanding arms that extend outwardly from a mounting base that mounts to a mold half The receptacle includes a bottom wall and a pair of spaced apart and generally parallel sidewalls that are spaced apart so as to define a pocket therebetween that receives the head when one mold half is being brought toward the other mold half The sidewalls are spaced apart so as to provide sufficient clearance for entry of the head while still accommodating some mold misalignment. In one preferred embodiment, the clearance between the head and pocket sidewall is at least 0.0005 inch to accommodate greater misalignment than a side lock.
In one preferred embodiment, each pocket sidewall has a tapered section adjacent the pocket mouth. Preferably, each tapered section tapers outwardly such that the width of the pocket adjacent its mouth is greater than the width of the pocket adjacent the bottom wall. Each tapered sidewall section of the receptacle bears against a corresponding tapered sidewall section of the head when the head is nearly completely inserted into the pocket to help correct misalignment. Preferably, when the head is inserted into the pocket, the tapered section of each head sidewall bears against a corresponding pocket sidewall such that there is zero clearance therebetween to help correct misalignment.
In a second mold interlock embodiment, the insert comprises a rectangular plate and each head sidewall preferably is equipped with only a single channel. To help prevent movement of the plate during mold operation, the lips of the channel converge slightly toward each other such that the channel is narrower on one end. The plate is of complementary construction such that it abuts against the lips during insertion and there is engagement between the lips and the plate that prevents lateral plate movement.
The plate is constructed so as to be replaceable, such as when wear warrants. In one preferred embodiment, the plate is intended to be sacrificial. In one preferred plate embodiment, the plate is comprised of a metal and includes spaced apart plugs embedded therein. Each plug preferably is comprised of a friction reducing material that can be a lubricant. For example, in one preferred plug embodiment, each plug is comprised of graphite. In another plate embodiment, the plate is comprised of a plurality of layers and can be of laminate construction. In one preferred plate embodiment, one of the layers comprises a friction reducing material that can be a lubricant.
In still another mold interlock embodiment, each head sidewall includes a second tapered section that is disposed between its free end and the straight sidewall section. The second tapered section is inwardly tapered such that the width of the head adjacent its free end is narrower than where the head sidewalls are straight. The second tapered section provides additional clearance that accommodates greater misalignment.
Objects, features and advantages of the invention include one or more of the following: to provide a mold interlock having improved wear resistance; to provide a mold interlock that tolerates mold misalignment while rapidly correcting the misalignment and providing protection to relatively small angle shut-offs; to provide a mold interlock that has replaceable wear surfaces for reduced operating costs; to provide a mold interlock that can be used in applications where liquid lubricants cannot be used; to provide a mold interlock that includes a reservoir for liquid lubricant that would ordinal be wiped free of the interlock during mold operation; to provide a mold interlock that is particularly well suited for use in plastic injection molding applications; to provide a mold interlock that achieves one or more of the benefits of side locks, tapered rectangular interlocks and round interlocks without one or more of their disadvantages; to provide a mold interlock that accommodates greater misalignment while still achieving zero clearance when completely seated; and to provide a mold interlock that is of simple, durable, robust, tough and economical construction and which is simple to install and use.